On my Alpha One,1991 Bayliner Capri 2050cx The exhaust bellows and u-joint bellows are in mint condition, I also have the new style shift cable, so yes I am able to replace the shift cable bellows on MINE in an hour with out ruining the cable itself, I also had advice from the man who works at NAPA, he has been a marine mechanic for 30yrs, Why he is at Napa now I really don't know and it really doesn't matter to me,Thats his business, But he really knew what he was talking about and helped me(I did all the work) but he is the one who showed me how to disconnect from the engine with shift forward and came out every 5 mins. to see how I was doing, On my boat YES it can be done and was!! without taking the drive off or ruining the shift cable and it was done in less than an hour in the Napa parking lot. This is what told me that yes it can be done.
http://www.mercstuff.com/shiftcablebellows.htm
And With help. I am only saying it can be done on my boat and was, still don't
know what drive you have either?? have you checked the S/N yet??